Interfacial features of TiAl alloy/316L stainless steel joint brazed with Zr−Cu−Ni−Al amorphous filler metal
Honggang Dong, Run-ze ZHANG, Yueqing Xia, Xiaohu Hao, Peng Li
Abstract
TiAl alloy and 316L stainless steel were vacuum-brazed with Zr−50.0Cu−7.1Ni−7.1Al (at.%) amorphous filler metal. The influence of brazing time and temperature on the interfacial microstructure and shear strength of the resultant joints was investigated. The brazed seam consisted of three layers, including two diffusion layers and one residual filler metal layer. The typical microstructure of brazed TiAl alloy/316L stainless steel joint was TiAl alloy substrate/α2-(Ti3Al)/AlCuTi/residual filler metal/Cu9Zr11+Fe23Zr6/Laves-Fe2Zr/α-(Fe,Cr)/316L stainless steel substrate. Discontinuous brittle Fe2Zr layer formed near the interface between the residual filler metal layer and α-(Fe,Cr) layer. The maximum shear strength of brazed joints reached 129 MPa when brazed at 1020 °C for 10 min. The diffusion activation energies of α2-(Ti3Al) and α-(Fe,Cr) phases were −195.769 and −112.420 kJ/mol, respectively, the diffusion constants for these two phases were 3.639×10−6 and 7.502×10−10 μm2/s, respectively. Cracks initiated at Fe2Zr layer and propagated into the residual filler metal layer during the shear test. The Laves-Fe2Zr phase existing on the fracture surface suggested the brittle fracture mode of the brazed joints.